The present invention generally relates to augmented reality and more particularly to a method for displaying an image of a scene outside of an aircraft in an augmented reality context. The invention also relates to an aircraft in which the cockpit is equipped with a display system for implementing said method.
With reference to FIG. 1, it is known to display on a screen 1 in the cockpit, such as for example the primary display screen (PDF, Primary Flight Display), a synthetic image in three dimensions of a scene 2 situated in front of the aircraft and upon which is superimposed an image comprising flight information 3 in order to enhance the image of the scene. Such a display, referred to as an augmented reality display or a synthetic vision display, makes it possible to give the pilot of the aircraft a better understanding of the environment outside of the aircraft, notably in bad weather or at night. The image of the scene comprises a terrain 4 and a generic blue sky 5 and the items of information about the terrain used for producing the image of the scene 2 are provided by onboard satellite positioning means combined with terrain databases. The items of flight information used for producing the flight information image 3 come from the avionics of the aircraft and notably comprise an FPV (Flight Path Vector) 6. The latter is conventionally a symbol representing an aircraft and indicates a point on the image of the scene 2 towards which the longitudinal axis of the aircraft is heading and is thus mobile on the screen as a function of the lateral and vertical movements of the aircraft.
Because of the small dimensions of the primary display screen 1, and in the case of the presence of strong side wind where the aircraft is in sideslip (a non-zero sideslip angle β between the air trajectory of the aircraft and its ground trajectory), the flight path vector 6 is not displayed on the screen 1 because it is situated outside of the field of vision of the terrain on the screen. However, the flight path vector 6 is an important item of information for guiding the pilot and it is necessary for it to be visible. In order to overcome this problem, processing means increase the field angle of the image of the scene 2, with a fixed image size. This being done, the image of the scene 2 represents a wider lateral extent of terrain and the flight path vector 6 then becomes visible on the screen.
The increase of the field angle reduces the magnification of the image of the scene 2 since the size of the latter remains fixed. When the field angle is too wide, the pilot is no longer able to make a comparison between the terrain of the image of the scene 2 displayed on the screen 1, which appears small and distant to him, and the real terrain which may be visible through the windows of the cockpit. The augmented reality display is therefore no longer usable.